The checklist to solve a malfunction

If your gas appliance has a plug, check whether there is power at the connected socket. For example, connect another device to the wall socket.
Are you not stressed? Check the stop in the meter cupboard.
Are the gas taps open under the boiler? What about the main tap in the meter cupboard?
Is the water pressure of the central heating system above 1 bar? If not: top up the water pressure to a maximum of 1.8 bar (see refilling).
Set the room thermostat to at least 30ºC and see if the boiler still turns on. If this is the case, there could be something wrong with the thermostat. Is the boiler not turning on? Report this as a malfunction.
Some gas appliances have a pilot light. Does this burn? If not, try lighting it again.
If your thermostat is equipped with batteries, the display will indicate whether they need to be replaced. Only alkaline batteries are allowed.
If the device has the option, reset. Unplugging and plugging back in can also work.
Important: make a note of the error code that can be read on the display and report it in the event of an error message.
If you do not have hot water at a tap while hot water comes from the tap elsewhere, there is a good chance that the aerator (the sieve) or the shower head is dirty.
It may happen that you have hot water, but the central heating does not work. Check that you do not have a dripping hot water tap.
This means that the gas appliance remains on hot water mode and does not switch to central heating.

What to do in case of a malfunction